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List of spacecraft instruments are selected to meet a mission's science goals.

Let's take New Horizons as an example and study the composition of Pluto's atmosphere, the shape and geological structures of the surface, and the particles interacting with the atmosphere From here.

In this case, we will need: several types of spectrometers, a radiometer, photo and video cameras, a particle recorder and a soil sample collector.

When the list of what we need is ready, what do we do next? Do we “go, select and buy” ready-made devices with suitable characteristics or design/develop/create the necessary tools from scratch? And is it possible for the device to be used in a situation that was not previously foreseen (for example, when it is necessary to study CMB, but there are no direct instruments for this on board)?

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    $\begingroup$ This would seem to be much better asked on Space exploration. However I think the answers "It depends". Most will be bespoke, some might be off the shelf. Yes, instruments get used in all sorts of ways that weren't foreseen. The people over on Space Exploration are likely to know more. $\endgroup$
    – James K
    Sep 26 at 17:17
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    $\begingroup$ @JamesK I'm pretty sure off-the-shelf tech is a rarity in spaceflight outside of cubesats. $\endgroup$
    – Darth Pseudonym
    Sep 26 at 20:24
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    $\begingroup$ I'm no expert, which is why I think this should go to [space] $\endgroup$
    – James K
    Sep 26 at 20:34
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    $\begingroup$ commercially-off-the-shelf (COTS) technology is being used - I'd recon in some parts at least. You won't always invent a new actuator, pump, FPGA or whatever; but you cannot buy a complete instrument off the shelf... Thus for a magnetometer you might buy COTS ring cores, qualify them and then build the flux gate magnetometer using these calibrated ones. The magnetometer isn't COTS, but parts of it are, and so will be screws, connectors etc $\endgroup$
    – planetmaker
    Sep 26 at 23:18

2 Answers 2

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Science spacecraft are custom-built, instruments tailored for the specific mission (and the mission custom-tailored to the available instruments - it's a inter-dependent process), taking into account the special requirements of (deep) space like resilent to large temperature variation, radiation-hardened, vibration-proof (during the launch) etc.

Usually the major space agencies make a call-for-proposal where teams of scientists submit a proposal for a mission along with the purpose of the mission, and drafts for the mission timeline and the needed instrumentation, arguments and proof that it is technically feasible, and where and who shall build them or at least supervise the building of the single instruments from the science side.You can see the studied proposals on the space agencies websites, e.g. here for ESA. As students there are cheaper opportunities which involve less long-term planning, but still you go through these phases on the fast track, like here from ESA.
These proposals are evaluated by the agencies and other scientists, and then a ranking of the submitted proposals is done - and the best (by whatever scientific and political criteria) are funded. Then the actual work begins and the winning teams have to actually start working on it, usually jointly with industry which receive a request for tender and the winner is contracted with detailed plans of what to build and a long list properties the instrument must fulfill and of verification criteria.

General requirements (e.g. some general mechanical ones like these):

3.4 Interfaces Requirements
3.4.1 Launcher Interfaces
3.4.1.1 The XXX flight hardware shall be compatible with the launch environment of SpaceX Dragon and Northrop Grumman Cygnus as defined in SSP 50835 [AD4].
3.4.1.2 The XXX flight hardware shall be launched packed in foam in non-operating, non-powered condition. 3.4.2 Spin Load The XXX Experiment shall be designed to withstand a roll rate at burnout of 8.0 Hz +/- 1 Hz at burnout of the motor.
Note: The static loads caused by the spin of 8 Hz can be calculated depending on the radius where the components of the experiments units are assembled.
Note: At motor burnout the linear acceleration will be at maximum.

etc etc and down to the individual parts, like cameras and optical setups where the requirements and performance matter:

3.2.9.3 The system shall have a resolution of at least 10"/pixel within the FOV.
Beginning of Note: The system does not need to resolve particles, only detect them. End of Note.
3.2.9.4 The system shall have a frame rate which is fast enough to allow for the tracking of the particles.
3.2.9.5 The exposure time shall be such that it matches the speed of the particles at the given illumination levels in order to avoid blurring.
3.2.9.6 The system shall be operated according to the reference experiment protocols defined in Section 4.1, in particular for what concerns operation durations and operations with other devices.
3.2.9.7 The two cameras shall be synchronised with each other. The simultaneousness shall be better than half of the inverse of the frame rate for frame rates of >10Hz and 0.05 sec for frame rates <10 Hz.
3.2.9.8 The sensitivity of the system shall be sufficient to detect the particles listed in Table 1.

Things like this are not available at your favourite home depot store.

Once the hardware is defined, the mission profile with detailed usage of instruments is discussed and agreed-upon often long before launch. The sequence of tasks is discussed and set in meetings with all involved scientists from all instruments and from flight dynamics (those who run the engines, telemetry home etc) - to find the scientific most promising way to operate the spacecraft given power, telemetry, fuel, spacecraft orientation, data storage and other limitations. Usually timelines are written down to the second, especially for the important maneuvers. Of course, as science advances and new opportunities arise, some things can be subject to change. Especially long missions don't do the detail planning of instrument use during the mission, but still year(s) in advance - possibly with some time at disposal by lead scientists to decide on short notice depending on circumstance.

So long story short: instruments are usually purpose-built, and only some parts will be off-the-shelf, if they fit the criteria. During the mission, all available data are gathered within the limitations of power, temporary storage and downlink bandwidth. You cannot modify the instruments once they're in space, you can at most change what the spacecraft looks at. But as instrumentation is purpose-built with a specific mission design in mind, other completely different uses often are not making good use of the ressources. If trade-offs in observation need to be made, this is discussed and decided in meetings of all involved parties who have instruments on board of the spacecraft, often long ahead of the actual time these observations are done.

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  • $\begingroup$ Thank you, very informative answer! I would like to clarify in what form the research group provides its proposal for mission equipment? Is it a road map, drawings and feasibility analysis, modeling results, or working prototypes that require significant improvements? $\endgroup$
    – dtn
    Oct 16 at 4:19
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It's complicated, but the general answer is that anything going into space is going to be, at minimum, heavily modified to handle the unique challenges of an environment that earthly tech doesn't usually manage, so there's not really any such thing as 'off the shelf technology' in that context.

Let's take a basic color camera, for example. For the purposes of this discussion, let's assume it's for use at close range, with visual light, under earth-normal lighting conditions -- a camera roughly equivalent to a human eye.

Even if they used a standard "off-the-shelf" CCD chip as the core of a camera, it's likely to need special lenses and filters to operate in space. It will probably need a radiation-hardened case, with special attention paid to thermal control (since you can't rely on ambient air for anything and it may need to survive extreme heat or cold from the environment). It may need a mount to aim and focus the camera, dust shields to keep grit out of it when not in use, and more. By the time you have a finished sensor, it's not really off-the-shelf anymore even if it started with a common piece of technology.

There's a point where you have to start defining what you actually mean by "off the shelf". Is there a tool you can just order online, receive, unwrap, and bolt onto your space probe? No, definitely not, not unless you're just building a cheap cubesat that you expect to last for a couple weeks. Are space probes going to use parts that can be ordered? Sure, of course they do. At what point does it cease to count as off the shelf technology, though? That's a gray area.

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  • $\begingroup$ Using the example of a video camera “from Earth”, you demonstrated what issues an engineer needs to solve when designing it for some kind of satellite. Do I understand correctly that such an engineer also needs to be a little bit of an astronomer or astrophysicist? $\endgroup$
    – dtn
    Oct 9 at 10:21
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    $\begingroup$ Well, your engineer needs to have information about the proposed operating environment, which is going to bring in questions about the intended orbit or planet it's heading for and potentially what the trip to get there is going to be like. A scientist may provide that information or you might use pre-published information a scientist came up with, and the engineer may end up picking up some of it by osmosis, but you don't really need special training other than in the sense that most anywhere you go outside earth is going to have some fairly wild conditions compared to our planet's surface. $\endgroup$
    – Darth Pseudonym
    Oct 9 at 13:44
  • $\begingroup$ "special training", are we talking about special training in the field of astrophysics and astronomy or engineering? $\endgroup$
    – dtn
    Oct 10 at 8:28
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    $\begingroup$ I mean you don't need special astronomical/astrophysical knowledge to work on equipment intended for use in space. If you can be told the radiation environment is thus-and-such and the heating situation is like this, then you should be able to work on the equipment without having to know how a star actually works (that is, astrophysics). $\endgroup$
    – Darth Pseudonym
    Oct 10 at 18:24
  • $\begingroup$ Maybe you're right. Especially in the case when, with the help of our astronomical instrument, we would somehow influence astrophysical processes and change them, then yes, we would need to understand them. $\endgroup$
    – dtn
    Oct 11 at 6:26

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